Culp married five times and was the father of three sons, Joshua (1958), Jason (1961) and Joseph (1963), and two daughters, Rachel (1964) and Samantha (1982).[4] From 1967 to 1970, he was married to Eurasian actress France Nguyen, whom he had met when she guest-starred on I Spy. She appeared in four episodes, two of them written by Culp himself.

Culp wrote scripts for a total of seven episodes, one of which he also directed. He also wrote scripts for other television series, including Trackdown, The Rifleman and The Greatest American Hero.

Culp died on March 24, 2010 while suffering a heart attack while taking a walk in Los Angeles, California. Culp's remains were buried in the Sunset View Cemetery in El Cerrito, California, located not far from his hometown of Oakland.